Tolerance to copper and zinc of Acidithiobacillus thiooxidans isolated from sewage sludge

The effect of copper and zinc ions on sulphur oxidation by Acidithiobacillus thiooxidans, strain SFR01, isolated from anaerobic sewage sludge was assessed, resulting in tolerance levels up to 20 and 200 mmol l(-1) for copper and zinc, respectively. The tolerance levels obtained were higher than the concentration of copper and zinc usually found in the collected sewage sludge. The tolerance levels obtained indicate no constraints for sludge bioleaching of those metals due to their toxicities to the indigenous A. thiooxidans.

A comparative study of the corrosion of high copper dental amalgams

Metallographic studies carried out for Tytin-Plus and Dispersalloy amalgams show a porous multiphase material, whose surface phases are: gamma-(Ag3Sn), gamma(1)-(Ag2Hg3), eta'-(Cu6Sn5) and epsilon-(Cu3Sn). Additionally, Dispersalloy is present in the Ag-Cu eutectic. The application of surface analysis by SEM reveal a heterogeneous distribution of the above mentioned phases. Microstructures consisting of colonies or clusters were not observed. The corrosion testing of these materials was done in 0.9% NaCl aerated solution at 25 degrees C using potentiodynamic polarization curves and ac impedance measurements. The corrosion process in these multiphase systems can be interpreted as the sum of more than one electrodissolution process and the posterior formation of corrosion films. on each electrode, the corrosion film is formed by different mechanisms. (C) 1998 Elsevier B.V. B.V. All rights reserved.

INTRATRACHEAL INJECTION OF NICKEL CHLORIDE AND COPPER-ZINC SUPEROXIDE-DISMUTASE ACTIVITY IN LUNG OF RATS

Superoxide radical (O2-) is a free radical that may be involved in various toxic processes. Cu-Zn superoxide dismutase catalyses the dismutation of the superoxide free radical and protects cells from oxidative damage, and it has been used clinically. The concentration of Ni2+ and Cu-Zn superoxide dismutase activity were measured in lungs of rats at time intervals of 5, 12, 19, 26, 33, and 40 days following an intratracheal injection of 127 nmol of NiCl2. Nickel chloride increased nickel content and resulted in a significant increase of Cu-Zn superoxide dismutase activity in lungs. This elevation of Cu-Zn superoxide dismutase activity was highest on the 12th day (approximately threefold) and is at levels comparable to controls rats on day 40 onwards. Since Cu-Zn superoxide dismutase activity was increased in lung throughout our experimental period without corresponding increases of Cu2+ and Zn2+, we speculate that the elevation of Cu-Zn superoxide dismutase activity might be due to an increased half-life of the enzyme, induced by nickel.

Ionic medium effects on equilibrium constants .1. Proton, copper(II), cadmium(II), lead(II) and acetate activity coefficients in aqueous solution

The molar single ion activity coefficients associated with hydrogen, copper(II), cadmium(II) and lead(II) ions were determined at 25 degrees C and ionic strengths between 0.100 and 3.00 M (NaClO4), whereas for acetate the ionic strengths were fixed between 0.300 and 2.00 M, held with the same inert electrolyte. The investigation was carried out potentiometrically by using proton-sensitive glass, copper, cadmium and lead ion-selective electrodes and a second-class Hg\Hg-2(CH3COO)(2) electrode. It was found that the activity coefficients of these ions (y(i)) can be assessed through the following empirical equations:log y(H) = -0.542I(0.5) + 0.451I; log y(Cu) = -1.249I(0.5) + 0.912I; log y(Cd) = -0.829I(0.5) + 0.448I(1.5);log y(Pb) = -0.404I(0.5) + 0.117I(2); and log y(Ac) = 0.0370I .

Synthesis and structural studies of (1,10-phenanthroline)(thiocyanate-N)-(triphenylphosphine)copper(I)

The compound (1,10-phenanthroline)(thiocyanate-N)(triphenylphosphine)copper(I), was synthesized and studied by IR spectroscopy and X-ray diffraction techniques. It is monomeric with the thiocyanate acting as a N-donor ligand. The copper atom shows a distorted tetrahedral coordination geometry.

Analysis of tolerance to copper and zinc in Aechmea blanchetiana grown in vitro

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

A Chloro-Bridged Linear Chain Imine-Copper(II) Complex and Its Application as an Enzyme-Free Amperometric Biosensor for Hydrogen Peroxide

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Controlled growth of anodic aluminium oxide films with hexagonal array of nanometer-sized pores filled with textured copper nanowires

Anodic aluminium oxide (AAO) films exhibiting a homogeneous morphology of parallel pores perpendicular to the surface were prepared in a two-step anodization process and filled with copper by electrochemical deposition. The optimum growth conditions for the formation of freestanding AAO films with hexagonal compact array of cylindrical pores were studied by field emission scanning electron microscopy and small angle X-ray scattering. The results show well-defined periodic structures with uniform pores size distribution for films with pore diameters between 40 and 70 nm prepared using different voltages and temperatures during the second anodization step. X-ray photoelectron spectroscopy and X-ray diffraction analysis of AAO films filled with copper show the formation of nanowires with high structural order, exhibiting a preferential crystalline orientation along the (2 2 0) axis and only small fraction of copper oxides. The best results for textured Cu nanowires were obtained at a reduction potential of -300 mV. (C) 2009 Elsevier Ltd. All rights reserved.

A Simple Method Based on ICP-MS for Estimation of Background Levels of Arsenic, Cadmium, Copper, Manganese, Nickel, Lead, and Selenium in Blood of the Brazilian Population

Throughout the world, biomonitoring has become the standard for assessing exposure of individuals to toxic elements as well as for responding to serious environmental public health problems. However, extensive biomonitoring surveys require rapid and simple analytical methods. Thus, a simple and high-throughput method is proposed for the determination of arsenic (As), cadmium (Cd), copper (Cu), manganese (Mn), nickel (Ni), lead (Pb), and selenium (Se) in blood samples by using inductively coupled plasma-mass spectrometry (ICP-MS). Prior to analysis, 200 l of blood samples was mixed with 500 l of 10% v/v tetramethylammonium hydroxide (TMAH) solution, incubated for 10 min, and subsequently diluted to 10 ml with a solution containing 0.05% w/v ethylenediamine tetraacetic acid (EDTA) + 0.005% v/v Triton X-100. After that, samples were directly analyzed by ICP-MS (ELAN DRC II). Rhodium was selected as an internal standard with matrix-matching calibration. Method detection limits were 0.08, 0.04, 0.5, 0.09, 0.12, 0.04, and 0.1 g//L for As, Cd, Cu, Mn, Ni, Pb, and Se, respectively. Validation data are provided based on the analysis of blood samples from the trace elements inter-\comparison program operated by the Institut National de Sante Publique du Quebec, Canada. Additional validation was provided by the analysis of human blood samples by the proposed method and by using electrothermal atomic absorption spectrometry (ETAAS). The method was subsequently applied for the estimation of background metal blood values in the Brazilian population. In general, the mean concentrations of As, Cd, Cu, Mn, Ni, Pb, and Se in blood were 1.1, 0.4, 890, 9.6, 2.1, 65.4, and 89.3 g/L, respectively, and are in agreement with other global populations. Influences of age, gender, smoking habits, alcohol consumption, and geographical variation on the values were also considered. Smoking habits influenced the levels of Cd in blood. The levels of Cu, Mn, and Pb were significantly correlated with gender, whereas Cu and Pb were significantly correlated with age. There were also interesting differences in Mn and Se levels in the population living in the north of Brazil compared to the south.

The characterisation of the protective film formed by benzotriazole on the 90/10 copper-nickel alloy surface in H2SO4 media

The nature of the protective film formed by benzotriazole (BTAH) on the surface of the 90/10 CuNi alloy in deaerated 0.5 mol L-1 H2SO4 solution containing Fe(III) ions as oxidant was investigated by weight-loss, calorimetric measurements, and by surface-enhanced Raman spectroscopy (SERS). The SERS measurements show that the protective film is composed by the [Cu(I)BTA](n), polymeric complex and that the BTAH molecules are also adsorbed on the electrode surface. A modification of the BET isotherm for adsorption of gases ill solids is proposed to describe the experimental results obtained from weight-loss experiments that suggest an adsorption in multilayers. Electrochemical studies of copper and nickel in 0.5 mol L-1 H2SO4 in presence and absence of BTAH have also been made as an aid to interpret the results. The calculated adsorption free energy of the cuprous benzotriazolate on the surface of the alloy is in accordance with the value for pure copper. (C) 2007 Elsevier Ltd. All rights reserved.

Copper resistance of biofilm cells of the plant pathogen Xylella fastidiosa

Xylella fastidiosa is a phytopathogen that causes diseases in different plant species. The development of disease symptoms is associated to the blockage of the xylem vessels caused by biofilm formation. In this study, we evaluated the sensitivity of biofilm and planktonic cells to copper, one of the most important antimicrobial agents used in agriculture. We measured the exopolysaccharides (EPS) content in biofilm and planktonic cells and used real-time reverse transcription polymerase chain reaction to evaluate the expression of the genes encoding proteins involved in cation/multidrug extrusion (acrA/B, mexE/czcA, and metI) and others associated with different copper resistance mechanisms (copB, cutA1, cutA2, and cutC) in the X. fastidiosa biofilm formed in two different media. We confirmed that biofilms are less susceptible to copper than planktonic cells. The amount of EPS seems to be directly related to the resistance and it varies according to the media where the cells are grown. The same was observed for gene expression. Nevertheless, some genes seem to have a greater importance in biofilm cells resistance to copper. Our results suggest a synergistic effect between diffusion barriers and other mechanisms associated with bacterial resistance in this phytopathogen. These mechanisms are important for a bacterium that is constantly under stress conditions in the host.

Mono and dinuclear Pd(II) complexes with pyrazole and imidazole-type ligands

The cyanate-bridged cyclopalladated compound [Pd(C(2),N-dmba)(mu-NCO)](2) (dmba=N,N-dimethylbenzylamine) reacts in acetone with pyrazole (pz), 3,5-dimethylpyrazole (dmpz), imidazole (imz) and 2-methylimidazole (mimz) to give [Pd(2)(C(2),N-dmba)(2)(mu-NCO)(mu-pz)] (1), [Pd(2)(C(2),N-dmba)(2)(mu-NCO)(mu-dmpz)] (2), [Pd(C(2),N-dmba)(NCO)(imz)] (3) and [Pd(C(2),N-dmba)(NCO)(mimz)] (4), respectively. The compounds were characterized by elemental analysis, IR spectroscopy and TG. The thermal decomposition of the compounds occurs in three consecutive steps and the final decomposition products were identified as Pd(0) by X-ray powder diffraction. The thermal stability order of the complexes is 2 > 3 > 1 > 4.